The Boston Celtics will be without Robert Williams III when the NBA season tips off as the 24-year-old recovers from offseason knee surgery The Boston Celtics will be without star center Robert Williams III when the season tips off next month. View the original article to see embedded media. Williams underwent arthroscopic surgery in his left knee to remove loose bodies and address swelling, the team announced Friday, adding it’ll be 8 to 12 weeks before Williams returns to basketball activities. Background Williams suffered a torn meniscus in March of last season that forced him to miss the end of…